Low/Mid Frequency Hum
 

New 2019 Audi A4 experiencing severely annoying low/mid frequency hum around sun roof when the following conditions are met:

1) A/C blower is on and internal air circulation is off (allowing outside air in)
2) Sun roof is completely closed
3) Low/Mid Frequency hum is generated around sunroof mechanism

Turn A/C blower off, hum stops

If I push the button to circulate cabin air (no outside air), the hum stops.

If if I open the sunroof (not slide it open but open it), the hum stops.

Any ideas as to what is causing this?

Given the conditions where you hear it, it sounds like the sunroof isn't completely sealed when closed. Air is trying to escape a crack in the seals and resonating.

Sunroof hum
 

I have a 2019 A4 with the same exact concern. Ever figure out a fix for this or what was causing the issue?

Hi Matt,

I’ve been traveling and haven’t had time to get it serviced. It does drive me a bit crazy.

Will let let you know what they find out - should be soon.

FIXED
 

Inspected the vehicle seals around the sunroof and all looked good. So I started checking the sunroof drains. BINGO! I found the passenger side sunroof drain valve distorted where it exits the body near the passenger side door hinge, allowing air to bypass into the area around the sunroof. Replaced the drain assembly and noise no longer present.

Awesome! Do I get a cookie?

Matt, was this something the dealer fixed? If so, is there a TSB for this?

I fixed it at the dealer. No TSB (yet). Check the drain hose valves. Fronts are near the front door hinges and the most likely suspects. Rears are harder to get to, they are behind the rear wheel well liners. They should look like they are sealed closed. If the flaps are distorted or torn, that could be your issue.

https://cimg5.ibsrv.net/gimg/www.aud...3fe8a7c5cd.jpg
DISTORTED PASSENGER WATER DRAIN
https://cimg8.ibsrv.net/gimg/www.aud...c54ce3b279.jpg
INTACT DRIVERS WATER DRAIN

Thank you! I’ll show this to my dealer. Will hopefully save a lot of time.